Questions tagged [seismic]

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1answer
58 views

Why do P waves have a higher velocity in the lower mantle than in the core even though the core has a much higher density?

I've just started teaching 9th grade Earth science and my students and I have noticed something about P and S wave depth vs velocity graphs. In the typical graph, eg: https://www.researchgate.net/...
0
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1answer
25 views

Hydrophone/geophone sensor sensitivity - noise versus signal

Today, a student asked this question, and I was unable to answer it in a way that was understandable and accurate - even for myself. For seismic data acquisition projects, how are sensors able to '...
1
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1answer
38 views

Using an accelerometer as a geophone to conduct a seismic survey

I am doing a capstone project for a sensor systems course and I would like to write a python program to acquire, process and present seismic data like that of seismic surveys. Is it possible using ...
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0answers
25 views

Finding out actual dip and dip direction of refractor

We have two traveltive curves for first arrivals (direct and refracted) from a dipping refractor in the forward and reverse directions along a profile line. my question is: Is there a logical way (non-...
0
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1answer
30 views

Is it reasonable to approximate the swinging building (base of the building) during an earthquake to a simple harmonic motion?

I am thinking of making a model of swinging building during earthquake and study the methods to minimize the swinging. So does it even makes sense to approximate the swinging buildings (the base of ...
3
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0answers
35 views

Seismic velocity inversion & analysis

I attended at talk recently at the TGS office in Houston, TX, by Marianna Raunch. During this talk, a statement was made that for "very large" velocity inversions, semblance (or other similar ...
3
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1answer
74 views

Wave train 200 m/s meaning

I ran a 60 m line intended for surficial seismic refraction. Energization with hammer. 12 (10 hz vertical 5 m spaced) geophones and 5 shots (15 m spaced). Record length 0.5 s. Thanks to a borehole ...
4
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1answer
70 views

wavelength of seismic wave with a gaussian source

i want to know how i get the wavelength/frequency of a seismic wave, if i only have a gaussian source and the velocity (c = 4000m/s) of a medium given. e.g. for a ricker wavelet it would be easy to ...
2
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1answer
26 views

Seismic amplitude distribution

Recorded (or raw) and processed pre/post-stack seismic data (relative amplitudes) usually display a standard normal distribution, albeit with a very small amount of skewness. What would be possible ...
1
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1answer
25 views

Seismic wavefield theory: velocity anisotropy

Does the reciprocity principle hold true in an anisotropic subsurface environment?
2
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1answer
54 views

What is the vertical axis of this waveform shown in this tweeted IRIS GIF?

This IRIS tweet shows a video of siesmic waves from the recent M6.4 Earthquake in California rolling across the US. I've made a small GIF to give the idea but the "GIF" in the tweet shows the whole ...
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1answer
56 views

How to read Seismic Survey?

Recently I am tasked to create a POC on detection of patterns using a neural . But I am from a computer science background so I know about neural networks but I don't have any knowledge about geology ...
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1answer
47 views

wave speed is smaller than both horizontal wave speed and vertical wave speed?

I am new to GIS and just get the idea of slowness. I can understand why people need the slowness in GIS rather than just the reciprocal of velocity. However, I feel the definition of slowness is weird ...
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0answers
15 views

Hi, is there good reference this raw earthquake data to covert into PGA, PGV and etc?

Is there good reference or software that these earthquake raw data will transform into strong ground motion such PGA, PGV and PGD. Thank you!
0
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0answers
72 views

3D fold coverage calculation

I have a configuration for which the nominal fold is 16 (i.e. 48 channel streamer, 1m group interval, 1.5m SP interval). I have been asked to calculate the fold coverage with the following criteria: ...
1
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1answer
47 views

reverse time migration for wave equation PDE using SBP-SAT

I'm stuck implementing a reverse time migration technique, the PDE(partial differential equation) being implemented is an acoustic wave equation, The numerical method being used is a FD(finite ...
2
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2answers
186 views

Travel Times for Seismic Wave Types - Why reflected t-x plot curves

I do not understand how the reflected wave in a seismic survey has a steepening slope (slows down) Please bear with me as I lay out my thoughts because I feel like I can grasp all of this except this ...
0
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1answer
59 views

Near-Surface Investigations: FWI vs. MASW

MASW is a common processing method for civil/geotechnical and even for oil/gas exploration (usually weathering static corrections) applications. In my experience, it seems to work well for most ...
3
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0answers
65 views

Seismic data acquisition: reliability of high-bandwidth data

In my research, finding and understanding info relating to the lower end of (conventional) surface seismic data acquisition (i.e. 15 - 1 Hz) is relatively simple. However, when I look at specs for a ...
1
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1answer
44 views

Love-Wave Propagation

Love-waves cannot exist in a half-space. Layering must be present and there also must be accompanied impedance contrasts associated with the layering. Because layering naturally induces seismic ...
2
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0answers
56 views

Difference between landslide waves and earth quake waves

I am new to this field, recently started working on landslide monitoring mainly in signal processing part. I have the following questions? 1.Will each land slide and every vibration have p wave, s ...
1
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1answer
219 views

Quality control in Seismic Acquisition - How much data is required?

When it comes to land or marine acquisition (oil exploration, for instance), I can see from literature that quality control (QC) is performed during the survey to ensure that the seismic traces ...
2
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1answer
611 views

converting segd data to SU format using seismic unix

I tried to convert segd format to su format using seismic unix by below command: segdread tape=1.segd > 1.su but I have an error: ...
2
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1answer
83 views

Basic petrophysics

The following question was inspired by Effective pressure or what is the effect of presssure?, which may be accessed here: https://inside.mines.edu/UserFiles/File/CRA/2005/...
2
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1answer
120 views

DC component in Hilbert transform concept for seismic data

In The Leading Edge tutorial article Phase and the Hilbert transform (Purves 2014), there is the following line: So we apply a Hilbert transform by multiplying all negative frequencies by i and all ...
4
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0answers
39 views

How do I generate a Moho depth model from seismic refraction data?

There are several permanent seismograph stations in Eastern Canada that have been recording arrival times for over 25 years. Using refracted Pn arrival times from natural earthquakes I would like to ...
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1answer
64 views

Spectral Whitening, Seismic Interferometry

What is the role of spectral whitening in the processing step done before cross-correlations in seismic interferometry?
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0answers
46 views

Seismology - PPV / VDV from geophone waveform data

I'm using an inexpensive seismometer to try and measure the effects of local HGV traffic on buildings. The device is connected to a Raspberry PI that has a Cirrus Logic Audio Card. The signal is fed ...
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2answers
626 views

Seismic dispersion: What does it really mean and what causes it?

Body waves (to some extent) and especially surface waves show dispersive characteristics during propagation. In Dr. Christopher Liner's book [Elements of Seismic Dispersion (2012)], this phenomenon is ...
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1answer
59 views

What does 'reghosted' mean in a seismic cube label?

I came across to a seismic volume labeled as reghosted. In my understanding, a seismic survey is deghosted as part of a processing step. Then I wonder why one would like to reghosted the data? Is ...
2
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0answers
36 views

Which wavelet for acoustic inversion?

If I have seismic data obtained with an explosive source (i.e. minimum phase wavelet), should I re-process the data into zero-phase data to perform an acoustic impedance inversion?
3
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1answer
227 views

Open source well information viewer

I am in the middle of a hobbyist experiment and would like suggestions on an open source HTML viewer for mud loggging, FMIs, lithology and seismic. I have used INT before but for this project I would ...
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0answers
47 views

Interpretation of horizon display

I am currently working on a project that involves using seismic attributes as input parameters in a neural network for estimation of porosity and permeability for a reservoir. Now, I need to correlate ...
0
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1answer
65 views

DC component: Seismic inversion

Multiple papers (for example, Limitations on impedance inversion of band-limited reflection data Gosh[2000]) and textbooks covering seismic inversion mention a necessary component of any seismic ...
2
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1answer
43 views

Seismic inversion: High-Frequency approximation

In numerous textbooks and papers, the phrase "high-frequency" approximation is used in regards to different types of seismic inversion. What exactly is meant by this? Also, what are the implications ...
6
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1answer
219 views

Seismic migration concepts

In Dr Hua-Wei Zhou's book Practical Seismic Data Analysis (2014), he includes and explains figures from previous classic works (i.e. Schneider, 1971) in order to describe migration from a fundamental ...
2
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1answer
333 views

Seismic AVO/AVA concepts

I have a basic question concerning AVO, AVA, and reflections. What is the difference between AVO/AVA and obliquity factors from a given reflection from a point in the subsurface? If there is a ...
3
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1answer
268 views

Which type of seismic sensors usually used in Earthquake Early Warning?

As I'm a newbie in seismology and related area, I would like to know which type of seismic sensors usually used in earthquake early warning systems?
4
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1answer
774 views

What is the relationship between raw seismic data, CMP Stacking, NMO & Machine Learning

I recently joined a geophysics project to assist with some of their machine learning modeling but am trying to gather the domain knowledge required to participate. Something I don't quite understand ...
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0answers
57 views

Problem in identification of seismic event?

I have taken the following synthetic seismogram, generated using Marmousi model, from the Madagascar website. I could not understand the origin of linear events (present in shot3 after 2 sec) and ...
1
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0answers
137 views

Does seismic anisotropy follow stratigraphy?

This question is in the context of velocity model building for reflection seismic imaging (between 0km and 10km in a sedimentary basin). This is really a rock physics question disguised as an imaging ...
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0answers
65 views

Theorist speculate about dozens of loud atmospheric booms across globe

Theorist speculate on the dozens of loud atmospheric booms across globe. Has any recognized institutions offered a plausible explanation as of now?
4
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1answer
244 views

Seismic data spectral analysis

The two images below correspond to two processed seismic cross-sections. My question is this: why at/near 0 Hz is there "lots" of seismic energy still present? Most if not all of the lower end of the ...
1
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1answer
74 views

What is seismic stretch in geophysical method?

What is seismic stretch in geophysical method ?
4
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1answer
3k views

SEGD and SEGY recorded data

What is the difference between a segd recorded data and a segy recorded data and can we convert from segd to segy and vice versa?
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0answers
356 views

Effects of Mexican Earthquake in San Andreas Fault Line

Could the recent 8.1 Magnitude Earthquake at the Cocos and Nazca plates off the Mexican coast have a knock on effect to the Pacific and Juan de Fuca Plates further north at the San Andreas Fault Line?
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3answers
2k views

What are the distinguishing features of an “artificial seismic wave” (e.g. a large underground explosion)

IN the NPR news item North Korea Possibly Conducts Sixth Nuclear Test, South Korea Says: The U.S. Geological Survey says it detected a 6.3 magnitude "possible explosion" near Sungjibaegam, North ...
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0answers
112 views

Linear vs nonlinear seismic inversion

I am using the MATLAB script BLIMP (Ferguson and Margrave, 1995) to invert SH-wave data for shear-impedance. Is this inversion scheme a linear or non-linear process? There are certainly non-linear ...
1
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1answer
83 views

Seismic Reflectivity and Fractal (Random) Behavior

*One of the fundamental assumptions of the convolutional model (and subsequently a lot of deconvolution methods) is that reflectivity is a purely random (or "white") process. Overall, the only ...
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0answers
47 views

Shear-Waves and Stress

-I study the near-surface via seismic reflection surveying with shear-waves. I know that effective stress strongly influences the velocity behavior of any body wave in the near-surface (5 - 50 m). My ...